The present invention relates generally to the fabrication of structures using three dimensional printing techniques and, more particularly, to the fabrication of complex structures, such as electromechanical assemblies, comprising two or more materials using three dimensional printing.
In today""s competitive marketplace, one of the keys to business success is the ability to shorten the time period between product conception and manufacture of a finished product suitable for delivery to a customer. Customer demand for a product may last for only a short time period, which is generally called the market window or window of opportunity for that product. Manufacturers that are unable to deliver a working product in the market window are at a severe competitive disadvantage with those companies that are quick to respond to market demands. A major component in the time required to transform a product conception into a finished article suitable for sale is the time involved in developing a functioning prototype.
In recent years, attention has been directed towards developing processes by which parts and tooling devices, such as molds and dies, can be rapidly fabricated to create functioning product prototypes. An example of such a process is the computer controlled, three dimensional printing technique disclosed in U.S. Pat. No. 5,387,380 to Cima et al. This patent discloses a process for making three dimensional parts in which a layer of powder (e.g., a powdered ceramic, a powdered metal, or a powdered plastic) about 100 microns thick is spread over a working surface. A single slice of the part or mold pattern is then printed into the powder by spraying a binder material onto the powder using specially designed ink-jet print heads. This process is repeated with each new layer being stacked on top of the previous layer. After the entire part has been printed, pressure or heat is applied to bond the layers into one uniform part. The excess powder that was not printed on is usually poured or shaken out of the part before any final heat or pressure treatment is applied. The entire process is controlled by a computer running a computer aided design (CAD)/computer aided manufacturing (CAM) program.
The CAD/CAM system ensures that the printing on the various layers corresponds with a computer model of the three dimensional part being formed.
While the aforementioned process is useful for rapidly prototyping three dimensional parts, there remains room for improvement in the art. Specifically, existing three dimensional printing techniques are limited to the fabrication of monolithic parts or structures. That is, the parts are derived from a single powdered material. As a result, existing three dimensional printing processes are not applicable for rapid prototyping of electromechanical devices. At best, the housing or shell of an electromechanical part can be prototyped using three dimensional printing with the remainder of the part being assembled using standard manufacturing procedures.
Accordingly, what is sought is a process by which electromechanical parts (i.e., parts having both conductive and dielectric components) can be prototyped using three dimensional printing techniques. It is further desirable that the process be capable of incorporating discrete, external components into the part during the printing process.
Certain advantages and novel features of the invention will be set forth in the description that follows and will become apparent to those skilled in the art upon examination of the following or may be learned with the practice of the invention.
To achieve the advantages and novel features, the present invention is generally directed to an improved process for making a structure using three dimensional printing techniques. Briefly stated, the method can be summarized by the following steps: A first type of powder material is deposited in a defined area to form a first layer. Next, a binder material is applied to certain regions of the first type of powder to define a portion of the structure to be formed. And finally, a portion of the unbound powder is removed using a technique such as vacuuming. The foregoing steps are repeated a sufficient number of times to create the desired shape of the structure as defined by the regions held by the binder material.
In accordance with an aspect of the invention, the binder material is either a metallic binder or a dielectric binder such that the structure contains electrical conductive regions where a metallic binder is applied and dielectric regions where a dielectric binder is applied.
In accordance with another aspect of the invention, external components can be incorporated into the structure during the printing process by inserting the components into evacuated regions that are formed during the powder removal step. Alternatively, components that are thinner than a layer of powder can be attached to a bound region (i.e., a region of powder with the binder applied) and then covered in a subsequent powder deposition step. As a result, a component can be incorporated into the structure such that it is entirely confined in a bound region of powder.
The present invention can also be embodied in a two powder process. In this regard, a second type of powder material that is different from the first type of powder material is also deposited in the defined area. A binder material is applied to certain regions of the second type of powder that further defines a portion of the structure to be formed. At least a portion of the unbound powder material is removed using, for example, a vacuuming technique. These steps are repeated as necessary until the completed structure is formed.
According to one aspect of the invention, the first and second powders are chosen such that the first powder material is a dielectric powder and the second powder material is a conductive powder.
The improved three dimensional printing process according to the present invention has many advantages, a few of which are set forth hereafter as examples.
Manufacturing costs for electromechanical structures are reduced as both conductive and dielectric regions can be formed in the structure during the printing process thus requiring fewer electrical connectors and/or wiring harnesses. Moreover, discrete components can be built in to the structure during the printing process, which eliminates further assembly steps.
Identification tags can be designed into structures using the improved three dimensional printing process of the present invention. For example, conductive and dielectric regions can be formed in the structure as a pattern of ones and zeros that can be read by a processor or a logic system as an identification code. Similarly, cavities and/or regions filled with a material having a higher atomic number on average than the remainder of the structure can be incorporated into the structure that would show up during an X-ray or ultrasonic examination. These types of identification tags are difficult if not impossible to alter without damaging the structure. Accordingly, the identification tags can be used to discourage theft or counterfeiting.